Toyota 2008 Prius Quick Reference Manual page 398

Engine/power control unit coolant
The coolant level is satisfactory if it is between the "FULL" and "LOW"
lines on the reservoir when the engine is cold.
Engine coolant reservoir
Power control unit coolant reservoir
PRIUS_U_(L/O_0802)
1
2
3
ITY43P012
1
2
3
LOW
ITY43P013
4-3. Do-it-yourself maintenance
Reservoir cap
FULL
LOW
If the level is on or below the
"LOW" line, add coolant up to the
"FULL" line.
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